JPS6333707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrophotographic apparatus that forms an electrostatic latent image on the surface of a photoreceptor drum, develops it with a developer, transfers it to a transfer material, and then cleans the surface of the photoreceptor drum and uses it repeatedly. It is related to.

Generally, this type of electrophotographic apparatus includes a cleaning member made of an elastic blade that is pressed against the photoreceptor surface of the photoreceptor drum, thereby cleaning the photoreceptor drum. However, some developer remains between the photoreceptor drum surface and the elastic blade, and while the machine is stopped and at rest, the developer pressurized by the elastic blade sticks to the photoreceptor drum surface, causing the next problem. When copying, it cannot be easily cleaned and black lines (so-called blade marks) appear on the copied image, which often significantly impairs the image quality. In order to solve this problem, it has been considered to improve the cleaning performance by attaching a web-like cleaning member to the rear of the elastic blade in the rotational direction of the photoreceptor drum or by swinging the elastic blade in its longitudinal direction. ing. However, although it is effective when the machine is stopped for a short time, when the machine is stopped for a long time, the developer adheres strongly to the surface of the photoreceptor drum, and a sufficient effect cannot be expected.
Furthermore, considering the durability of the web-like cleaning member, it is necessary to convert it against dirt and to roll it up so that it always comes into contact with a new web surface, which is complicated. Further, it is not preferable to give swinging motion to the elastic blade because the displacement to which the edge of the elastic blade is subjected will not be constant and the life of the edge will be shortened. Increasing the cleaning performance by increasing the pressure will of course have the opposite effect in that it will forcefully push out the adhesion, and weakening the pressure will prevent blade marks from occurring, but at the same time it will This reduces cleaning performance and becomes a problem.

As a result of research into the mechanism by which such blade marks occur, the present invention attempts to fundamentally solve the problem by removing the factors contributing to this generation mechanism.

In order to achieve such an objective, the present invention
Even after copying is completed and the residual developer on the photosensitive drum is removed by the elastic blade that is in pressure contact with the photosensitive drum, the photosensitive drum continues to rotate for a while and the elastic blade separates the photosensitive drum and then the photosensitive drum is removed. This provides an electrophotographic apparatus that can be stopped. Although the mechanism behind the generation of blade marks in such electrophotographic equipment has been removed, the reason for this can be determined based on experiments.
This will be explained below with reference to FIG.

First, in FIG. 1, when the cleaning member, that is, the elastic blade 2 is separated from the photosensitive drum 1 that has stopped after copying is completed, and the surface of the photosensitive drum that the elastic blade 2 was in pressure contact with is looked at, it can be seen that three residual developers Thin lines 3 (intervals of about 0.5 mm) may be observed. Of these three lines, the first line A in the drum rotation direction is due to the developer that has gone around to the back of the edge of the elastic blade, and the last line C
is a line caused by the developer accumulated in front of the elastic blade when the photosensitive drum has stopped. Both of these can be easily wiped off. However, the middle line B is the previous A, C2
It is difficult to wipe off compared to the line, and it can be assumed that this is due to the developer that has gotten under the nip due to the pressure applied by the elastic blade. If this line B remains in contact with the elastic blade for a long period of time, it will form a so-called blade mark that will stick to the surface of the photosensitive drum. However, although the details of how these three thin lines are generated are not known, they tend to occur when the friction between the elastic blade and the surface of the photosensitive drum increases. Also, as mentioned above, the fine line B is affected by the pressing force of the elastic blade, but even if you simply apply developer to the surface of the photosensitive drum and then leave it in pressure contact with the elastic blade, blade marks will still occur. It was found that blade marks were generated only when the photosensitive drum was left in pressure contact with the photosensitive drum in a pattern in which the photosensitive drum rotated and then stopped while the elastic blade was in pressure contact. This is because when the photosensitive drum rotates or stops, the friction (maximum static friction) between the elastic blade and the surface of the photosensitive drum increases, and the residual developer in front of the elastic blade is collected under the nip of the elastic blade that is in pressure contact. It was predicted that the photosensitive drum would easily stick to the surface due to the effects of frictional heat between the photosensitive drum and the elastic blade due to the rotation of the photosensitive drum.This combined with the pressure contact force of the elastic blade when the photosensitive drum was stopped caused the photosensitive drum to become sticky. It is presumed that it is something that sticks to the surface.
Therefore, blade marks can be prevented by releasing the pressure contact of the elastic blade before the photosensitive drum stops rotating. Further, even if the elastic blade is separated immediately after the photosensitive drum stops rotating, blade marks may be left. However, the occurrence of blade marks as described above is not limited to dry electrophotography, but also applies to electrophotography using a liquid developer. In particular, in the case of liquid developer, when the machine is stopped, the liquid developer remaining in front of the elastic blade evaporates and sticks to the surface of the photosensitive drum, so it is not cleaned during the next copy and may damage the elastic blade or the surface of the photosensitive drum. It was thought that traces were generated. In order to improve this point, it has been considered to supply a cleaning liquid such as a developing liquid in front of this elastic blade to infiltrate the stuck substances before starting cleaning. However, although it is effective in infiltrating the residual developer stuck in front of the elastic blade, it is not effective at all against the developer caught between the elastic blade and the photosensitive drum that are pressed against each other. In fact, even if the machine was left unattended with only the cleaning liquid being supplied even after the photosensitive drum stopped after copying was completed, blade marks still occurred. Therefore, it has been found that blade marks can be prevented by releasing the pressure contact of the elastic blade before the photosensitive drum stops rotating. However, when separating the elastic blade from the photosensitive drum, it is preferable to first stop the developing device and the supply of cleaning liquid, and then continue rotating the photosensitive drum until the amount of developer in front of the elastic blade becomes sufficiently small before separating it. .

As described above, the present invention provides an electrophotographic apparatus in which an electrostatic latent image is formed on the surface of a photoreceptor drum, developed with a developer, transferred to a transfer material, and then the photoreceptor drum surface is cleaned and used repeatedly. , a cleaning member made of an elastic blade is provided in pressure contact with the photoreceptor drum during recording, and a device is provided for separating the elastic blade from the surface of the photoreceptor drum while the photoreceptor drum is still rotating after recording is completed. The present invention provides an electrophotographic apparatus characterized by the following.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic apparatus using a dry developer will be described with reference to FIG. In FIG. 2, reference numeral 1 denotes a photosensitive drum, which rotates in the direction of the arrow. 2 is an elastic blade held in a blade holder 4, and this blade holder 4 is fixed to a lever 6 that rotates in an arc around a fulcrum 5. The other end of the lever 6 is connected to a plunger 7 and a spring 8. The distance between the elastic blade 2 and the photosensitive drum 1 is determined by the distance between the elastic blade 2 and the photosensitive drum 1. The rotation of the photosensitive drum continues until the transfer residual image developer on the drum surface is scraped off by the elastic blade 2 and the photosensitive drum surface becomes clean. For example, a post-rotation signal is sent to erase and equalize the latent image potential on the photosensitive drum surface. By turning the plunger 7 OFF, etc., the spring 8 moves the lever 6 around the fulcrum 5. The drum rotation then stops.

As described above, the present invention provides clean copies free of blade marks by eliminating the mechanism by which blade marks occur.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for explaining the present invention, Figure 2 is an explanatory diagram for explaining the present invention;
The figure is a side view showing one embodiment of the present invention. 1...Photosensitive drum, 2...Elastic blade, 3...
...thin line due to residual developer, 4...blade holder, 5...fulcrum, 6...lever, 7...plunger, 8...spring.

Claims (1)

[Claims] 1. In an electrophotographic apparatus that forms an electrostatic latent image on the surface of a photoreceptor drum, develops it with a developer, and transfers it to a transfer material, the surface of the photoreceptor drum is cleaned and used repeatedly, during recording on the photoreceptor drum. A cleaning member consisting of an elastic blade that comes into pressure contact is provided, and while the photoreceptor drum is still rotating after recording is completed,
An electrophotographic apparatus, further comprising a device for separating the elastic blade from the surface of the photoreceptor drum.